The present invention relates to a shaft support structure which maintains a rotation accuracy of a rotation shaft and simplifies a structure, a laser beam projecting unit including the shaft support structure and a surveying instrument including the laser beam projecting unit.
A rotation unit of a precision machine such as a surveying machine or the like requires a high rotation accuracy, and a runout of the rotation shaft requires an accuracy by a unit of a second.
In order to achieve this high accuracy, in a shaft support structure of a conventional rotation shaft, the rotation shaft is supported by two bearings, a spring is provided between the two bearings, the spring applies a pressurization for getting closer to or for leaving away from to the two bearings and a gap present in the bearings is suppressed.
For this reason, the number of components is large, a structure of a shaft support portion becomes large-sized, and further, each component requires the high accuracy and thus, a manufacturing cost increases.